Dynamo-electric apparatus



O. F. BRUSH. Dynamo-Electric Apparatus.

No. 224,511. Patented Feb. 17, 1880.

M czM/ 2 $5; QZTATTORNEYS UNITED STATES PATENT OFFICE.

CHARLES F. BRUSH, OF CLEVELAND, OHIO.

DYNAMO-ELECTRIC APPARATUS.

SPECIFICATION forming part of Letters Patent No. 224,511, dated February 17, 1880.

Application filed November 21, 1879.

To all whom it may concern:

Be it known that I, CHARLES F. BRUSH, of Cleveland, in the county ofOuyahoga and State of Ohio, have invented certain new and useful Improvements in Dynamo-Electric Appa ratus; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it pertains to make and use it, reference being had to the accompanying drawings, which form part of this specification.

My invention relates to dynamo-electric machines, and has for its object the adaptation of such machines to variable external conditions without variation of the speed at which their armatures are rotated, but by variation of the intensity of the magnetic field, and this by means not directly depending on thetvolume of current circulating in the external circuit.

\Vhen dynamo-electric machines ofusual construction are driven at a normal speed, the external or working resistance must be of certain amount in order to secure a normal volume of current in circulation. Any addition to the work to be performed or increase of external resistance is attended by a diminution of the current strength, while any decrease in the resistance of the external circuit is productive of an increased volume of current. In

other words, the current produced by these machines varies inversely as the work they are called upon to perform.

It is generally desirable and often necessary that the volume of current maintained in circulation by a machine should remain nearly constant, while the external or working resistance is varied within reasonable limits to eonform to variable requirements. This end has heretofore been attained by varying the speed at which the armature of the machine is retated. This method is generally impracticable, especially when many variations of external conditions are encountered.

I effect my object by varying the intensity of the magnetic field in which the armature rotates. Suppose a machine driven at its normal speed maintains its normal current through a certain external resistance. N ow, if this resistance is diminished, and at the same time the intensity of the magnetic field of the machine is also diminished a certain amount, then the current in circulation will remain the same as before, because its electro-motive force has been lowered. T

The magnetic field of the machine is weakened either by shunting away from the coils of the field-magnets a portion of the current which excites them, or by cutting out or shortcircuiting some portion of one or more of the coils, so that the current shall make a less number of convolutions about the cores of the magnets. By varying the resistance of the shunt which divert-s a portion of the current from the magnet-coils, or by varying the number of eonvolutions of the coils cut out or short cireuited, any number of variations in the intensity of the magnetic field of the machine may be produced.

In the drawings, Figure 1 represents a portion of a dynamo-electric machine provided with a shunt of manually-adjustable resistance around the field-magnet circuit. Fig. 2 represents a modified embodiment of my invention, wherein its operations are performed in an automatic manner. Figs. 3, i, and 5 show other similar modifications. Fig. 6 represents a field-magnet coil adapted to have various portions of itself short-cireuited. Fig. 7 shows a modification of the same. Fig. 8 represents a magnet-helix adapted to have various portions of itself out out of the circuit.

In Fig. l, A A represent the two helices of one of the magnets of a dynamo-electric machine. They are joined togetherin single circuit, and one end of the conductor so formed is attached to the commutator-brush B, while the other end is attached to the binding-post I forming one terminal of the machine. The other binding-post or terminal, N, is connected with the remaining commutator-brush G.

a b o d e are resistance-coils connected with each other in series by means of the studs or buttons to I) c, &e., the coil to being also connected with one end of the field-magnet conductor at P.

D is a switch-arm, pivoted at g, and adapted to connect 9 with a b c, &c., at pleasure. The stud g is connected with the commutatorbrush B, and thus with the other end of the magnet circuit.

Now, when the terminals PN are connected by means of the external or working circuit (not shown) all of the current developed by the machine in operation will circulate in the helices A. A so long as the switch-arm D is not in contact with any of the buttons at 7) c, &c.; but when the arm D is moved into eontact with the button a, then a portion of the current developed by the machine will be diverted from the helices A A, and will flow through the shunt-circuit P a (5 D g B, the amount so shunted being determined by the resistance of the shunt-circuit as compared with that of the magnet-circuit. The machine will now be in a condition to develop its normal current through a small external resistance only, beeauseits field-magnets are greatly weakened through the decrease of the current exciting them.

The coil a is made of such resistance that when it only is included in the shunt-circuit the machine shall be adapted to operate normally the smallest external resistance met with in practice.

)Vhen the arm D is moved to the button Z) the resistance 1) is added to the shunt-circuit, whereby less current is diverted from the magnet-circuit, the intensity of the magnetic field is increased, and the machine is adapted to operate an increased external resistance. By moving the arm D to c, &c., and thus adding the resistances c, &c., to the slmnt-circuit, the machine will in like manner become adapted to operate more and more external resistance, until, finally, when the arm I) is moved off from the last button, 6, (the resistance of the shunt-circuit being new infinitely great,) the machine will have attained its full power.

In order to adapt the machine to regularlyincreasing external resistances the resistances b c d c are made successively greater, because each one, in order to increase the total resistance of the shunt in a given proportion, must obviously be larger than the one preceding it. Thus the last resistance after 0 (circuit open) is infinitely great.

Obviously one or more (preferably all) of the magnet-helices of a machine may be included in that part of the circuit of the machine attected by the shunt.

In practice I find it convenient to arrange the resistances a Z) 0, &c., on metal cores in a metal case, and connect the piece of apparatus with the dynamo-machine by means of suitable wires. The metal of the cores and case absorbs the heat developed in the resistance coils, and dissipates it by radiation and convection. I also provide the metal case surrounding and protecting the resistance-coils with suitable openings above and below to allow a circulation of air about the coils, which arrangement materially aids in keeping them cool.

My invention is welladapted for use with dynamo-electric machines operating several electric lights in single circuit, since by means of this device such machines may operate normally any number of lights from one (the other lights being short-circuited) up to their full capacity withoutchange of speed, and with an absorption of driving-power varying (though not proportionally) with the number oflights used. It may also be applied to electroplatingmachines, and with excellent results.

Fig. 2 of the drawings illustrates a method of operating the switch-arm D automatically, according to the varying requirements of the working circuit of the machine.

The arm D is held in the position shown in the figure by means of the springH, so that the shunt-resistances are open-eircuited when the machine is operating its highest external resistance. An armature is attached to a short prolongation of the arm D in front of an eleetro-magnet, E, which is excited by the;

working current from the machine, as shownj) The tension of the s n'ingJIi'is so adjusted that it shall bejust sufficient to hold the arm D in the position shown when the current exciting the opposing magnet E is of normal amount.

Now, it the external or working resistance of the machine is diminished, the first efiect will be an augmentation of the volume of current in circulation; but this will at once in crease the attraction of the magnet E for its armature, and the arm 1) will be thrown successively into contactwith the buttons 0, (1., &c., until the shunt-resistance is sufliciently reduced to efiect the reduction of the general current nearly to its normal condition in the manner already specified. Conversely, an increase of resistance in the working circuit will first diminish the current in circulation, the magnet E will become weakened, and the opposing spring H will throw the arm 1) in the other direction until the increasing resistance of the shunt produces a sulficiontlyincreased working current to enable the magnet E to arrest the action of the spring.

Fig. 3 shows a modified form of automatic shunt-resistance. The resistances a, I), c, &c., of Figs. 1 and 2 are here replaced by a pile, H, of carbon disks or plates, the resistance of which is varied by varying pressure brought to bear on the pile through the agency of the magnet E, the latter being excited by the working current from the dynamo-1nachine, as described in connection with Fig.

The operation of the device is obvious without further explanation.

Figs. 3, l, and 5 show obvious modifications of the resistancepile H, Fig. 3.

Instead of employing a fixed magnet-core and movable armature in these automatic devices, the magnet-helix may be made hollow, and a movable core may be substituted for the armature.

Means other than magnetism may also be employed to effect these automatic operations-such, for instance, as varying expansion in wires, bars, or ribbons of metal, produced by varying temperatures of such bodies, due to varying currents passing through them.

Automatic variations of the magnetic field of a dynamo-electric machine corresponding to Varying external or working resistances may also be effected by means of a device shown and described in Letters Patent No. 217,677, granted to me July 22, 1879, and known as a teaser. The action of this device for this purpose is obvious: the greater the resistance of the working circuit of the machine the greater amount of current will be shunted through the teaser, thus strengthening the magnetic field of the machine accordingly.

Instead of shunting away a portion of the current used to excite the magnets of a dynamoelectric machine, in order to reduce the mag netic field of the latter, some of the convolutions of the magnet-helices may be short-circuited, or cut out of the circuit altogether, thus reducing the magnetism by reducing the number of current convolutions. lhismethod may be applied to one or several of the field-offorce helices of a machine.

Fig. 6 of the drawings shows an end view of a field-magnet core and helix. A portion of the m aguet-head is represented as cut away, thus exposing the convolutions of helix-conductor to view. Now, by inserting one or more metallic pins or plugs between the convolutions of wire, as shown in the figure, a suitable number of layers of the wire may be short-circuited (and thus rendered inactive) to effect the purpose in "iew.

Fig. 7 shows a modification of Fig. 6, wherein the short-circuiting plugs are replaced by a switch-arm connected with the outer convolution of wire, and adapted to make contact with various other convolutious, thus shortcircuiting all of those convolutions or layers of wire which lie between.

Fig. 8 shows a modification of the device shown in Fig. 7, wherein the switch-arm itself forms the terminal of the helixconductor, thus determining the number of convolutions of the working helix according to its position, the remaining idle convolutions being opencircuited.

Thedevices shown in Figs. 6, 7, and 8 may be rendered automatic in their action by means analogous to that shown in Fig. 2.

What I claim is 1. A dynamo-electric machine constructed or combined with suitable device for primarily varying the strength of the current exciting its field-of-forcc electro-magnets.

2. In a dynamo-electric machine, the combination, with one or more of its inducing or field-of-force electro-magnets, of an adjustable resistance, whereby the strength of the current applied to said magnets may be determined, and governed, and varied, substantially as and for the purpose shown.

3. In a dynamo-electric machine, the combination, with one or more oi its inducing or field-of-force electro-magnets,-of a shunt-circuit, within which is included an adjustable resistance for varying the strength of the current applied to said magnets.

In testimony whereof I have signed 1n y name to this specification in the presence of two subscribing witncsses.

CHARLES F. BRUSH.

Witnesses:

JNo. GRowELL, Jr., LEVERETI L. LEGGETT. 

